Cooling, neutralizing, and purifying the gaseous products of combustion poses a serious world-wide challenge. Alternative fuels, such as waste oil (and other used petroleum based substances), tires, wood, and coal, although ideal furnace fuel in that they are inexpensive and abundant, emit large amounts of dense, toxic pollutants when burnt. In this era of "acid rain", "global warming", and record smog levels, the emission of such pollutants is recognized as contributing to problems that are detrimental to all living things.
Waste oil furnaces, tire burners, and wood and coal stoves have been banned in some areas due to the high levels of dense and toxic pollutants, including NOx and SO2, given off by these devices. The 1990 Clean Air Act approved by Congress establishes even more stringent air quality standards. Addressed in the 1990 Clean Air Act is the problem of "acid rain" which is caused primarily by the emission of acidic gaseous waste products of fossil fuel combustion.
In addition, waste oil is not easily and economically disposed of by means other than combustion. Alternatives to burning waste oil for heat, generation of power, etc., include illegal dumping and underground or underwater storage methods, all of which pose the threat of contaminating soil and water supplies.
The economical disposal of used tires is also somewhat limited to combustion, as tire piles present a serious fire hazard, promote the breeding of insects and disease, and are not easily buried due to their tendency to "float" to the surface.
Wood and coal stoves both serve as inexpensive alternatives to electric or gas heat.
Methods and apparatus for cleansing and neutralizing combustion fumes are well known to those skilled in the art. Some examples are L. J. Kinney, July 28, 1970, U.S. Pat. No. 3,522,000, B. E. Arnesjo, Oct. 6, 1970, U.S. Pat. No. 3,532,595, and Holl, Mar. 11, 1975, U.S. Pat. No. 3,870,082.
The above mentioned prior art discloses that it is well known toxic fumes can be treated by a method of stages to remove suspended particles.
Both the Kinney and Holl patents et. al. disclose the use of a series of screens, barriers, and baffles wetted by a water mist to trap and collect solid particles suspended in combustion fumes. These arrangements have a serious limitation, especially in the case of scrubbing waste oil combustion exhaust, as waste oil may contain up to 20% contaminants. Waste oil and tire combustion emissions contain unusually large, dense, particulates which would quickly clog and obstruct any such physical barrier or filtering device. This situation would be exaggerated by spraying any such filters or screens with a water mist, thereby causing the heavy particulates to become viscous, as is the case with both the Kinney and Holl devices.
Prior apparatuses, such as the Holl and Kinney devices, have disclosed methods of capturing particulates in exhaust by means of contacting the fumes with a fine water mist spray, thereby causing the particulates to coalesce onto water droplets. These particle-laden droplets are collected onto a baffle, plate, screen, or other such physical barrier, and allowed to drip into a pool of water below. Such methods are exclusively effective on fumes containing sub-micron particles and not for use with dense, particulate-heavy exhaust. Such methods would not actively capture and dilute or dissolve dense particulates, and would cause clogging and inefficiency in the apparatus.
Neither the Holl nor the Arnesjo models disclose a method of slowing and removing large debris from exhaust fumes prior to entering the water-related aspects of the apparatus. Thus, even the largest particles would be allowed to enter these devices and clog the barriers, screens, filters, and pumps.
Because the Kinney and Holl models utilize a method of physical barriers which obstruct the flow of exhaust through the devices, draft boosters such as the large fans disclosed by Kinney and centrifugal draft booster disclosed by Holl, are required to force gases through the cleansing apparatus and to avoid overheating, possibly damaging the device, or creating a fire hazard.
The Holl patent discloses a method of physical barrier filters, but does not provide adequate draft or cooling to accept the combustion fumes of materials such as waste oil and tires. Using the Holl design to cleanse such super-heated exhaust would result in the apparatus quickly overheating, risking damage to the apparatus and presenting a serious fire hazard.
The Holl model in particular lacks an accurate method of controlling the temperature of the accumulated water in the bottom of the device. Super-heated exhaust entering the apparatus could quickly cause the water to boil; the only method for cooling the accumulated water is to add fresh tap water and dispose of the heated waste water, diminishing the efficiency of the furnace to which the apparatus is attached and increasing costs associated with water consumption.
Neutralization of waste oil exhaust fumes with alkalines such as ammonium hydroxide and calcium hydroxide would not be effective in the Holl or Arnesjo models as the temperatures within these apparatuses could not be accurately maintained at a predetermined level for such neutralizing reagents to remain in solution.
Calcium hydroxide is an inexpensive, accepted, and active substance used to neutralize sulfur dioxide and nitrous oxide. The solubility of calcium hydroxide decreases with an increase in the temperature of an aqueous calcium hydroxide solution.
Ammonium hydroxide, another alkaline used to neutralize sulfur dioxide and nitrous emissions, will be separated out of an aqueous solution by boiling.
Therefore, it is important that the temperature inside such an apparatus be monitored and accurately controlled so that the neutralizing reagents remain in solution.
Waste oil burns in excess of 2200 degrees Fahrenheit. It is typical for the exhaust emitted by waste oil furnaces to exit the furnace at 900 to 1000 degrees Fahrenheit. Tires burn in excess of 3000 degrees Fahrenheit. Such intense temperatures require an exhaust scrubber to have an extremely strong draft and effective cooling mechanism to prevent damage to the apparatus and to avoid creating a fire hazard.
Water is capable of absorbing far more calories than metal or air and is preferable for use in cooling; the Holl and Kinney models depend primarily on metal casing and air draft, rather than water, to cool super-heated exhaust. The Arnesjo model does not attempt to cool combustion fumes.
Neither the Kinney, the Arnesjo nor the Holl apparatuses attempt to utilize combustion exhaust-heated water to increase the efficiency of the furnace to which it is attached. The heat of the exhaust is "wasted" by the Holl and Kinney apparatuses as the fumes simply pass through the unit and are not utilized for any valuable purpose.
Waste oil furnaces, tire burners, and wood and coal stoves are typically small in size and are utilized, in large part, for their cost effectiveness to individuals and businesses for whom the use of such devices is economical as compared to other sources of heat. Thus, the subject invention would only be practical if it could be produced for a reasonable price, easily maintained and cleaned, and accommodated in a relatively small amount of space.
The Arnesjo model would have to be relatively tall to be effective as each set of jet nozzles therein is located one on top of the other and would require space for mixing and leaching. Draft in the Arnesjo model is dependent on the natural tendency for hot air to rise and on a large amount of air space through which the exhaust may travel. Therefore, the Arnesjo device could not be significantly reduced in size and still maintain efficiency. This apparatus was specifically engineered for the purpose of producing hot water and was not designed for scrubbing, cooling or neutralizing dense, high-particulate emissions. The Arnesjo device would be expensive to manufacture due to the size and number of pumps, the very large and cumbersome size of the apparatus, and the difficultly of cleaning and maintaining the unit, making it impractical and cost-prohibitive for the average alternative furnace owner.